The first Queen's Speech of Gordon Brown's premiership is his chance to regain the political initiative. This depends on joining the dots across his legislative programme to paint a public picture of the Britain he wants to help shape.

A decade-old government cannot see off calls of "time for a change" by sticking to "more of the same". Mr Brown's own change agenda must build on areas the Government got right during his decade as Chancellor. He must also explain why key issues, notably climate change and housing, need a greater priority in the next decade than the last.

And a new premier must seize the chance to start again on civil liberties and foreign policy: where Tony Blair lost the ability to get a public hearing, Mr Brown's well-received lecture on liberty was a significant olive branch. Differences over detention powers might now be debated in an atmosphere of mutual respect. A willingness to reopen ID cards to scrutiny, where "case not proven" would be a generous verdict, could build on this.

Mr Brown needs a distinctive policy agenda because he will need to fight a different Labour campaign next time. He must reject advice to "stick to a winning formula" – he cannot win the next election using the 1997 war book.

Of course, Labour must win swing voters in the super-marginals, but it would be a dangerous mistake to think that 8,000 voters in marginal seats will decide the result, as the Electoral Reform Society claims. Labour's electoral coalition risks fracture on three fronts. Winning swing votes will be in vain if Labour has not also got its working-class vote out and reconnected with disillusioned liberal opinion, too.

There are "heartland" and liberal voters in every marginal seat. A party of government cannot have a "sticking plaster" coalition that makes different arguments to each group – it must address the issues that can bind this coalition together, notably housing, support for parents and childcare, and extending educational opportunity

Several arguments that have served Labour well will be weaker by 2009. The 1997 mantra was "kick the Tories out". In 2001, the call for more time to complete the job ("a lot done, a lot to do") caught the mood. In 2005, Michael Howard made Labour's argument – "the nasty party hasn't changed". Now, memories of Tory sleaze have faded. The Government will be 12 years old, and everything David Cameron does is intended to send the message that his party has changed.

Since 1997, the case for caution has prevailed among Labour strategists – the "vision thing" seen as an electoral risk Labour cannot afford. Now it is a matter of necessity and political survival, not just centre-left desire.

Mr Cameron's strategy is to be seen signing up to progressive language and Labour spending plans, so voters think there is little risk in putting fresh faces into government. Mr Brown will find himself in the campaign his opponent wants unless he ensures there are clear dividing lines.

Gordon Brown has a vision, but it sometimes seems that you have to work in a think-tank and talk about "progressive universalism" to get it. He must translate policy ideas into the language of public arguments and election posters. He should explain why his moral purpose in politics is defined by extending opportunity to all and narrowing the gaps in life chances in Britain, because we are stronger as a society and an economy when all are included.

"Reform" will continue, but ministers must talk more about the social ends that reforms serve. This Prime Minister, unlike Tony Blair, will say that "the gap matters". He should now turn the policy agenda into the progressive causes and campaigns for this generation: that no child should grow up in poverty in this affluent society; that pupils in state schools should enjoy similar opportunities to those educated privately; that work should earn a living wage and we must invest in the skills of all to avoid being losers in a global economy; that we should not die sooner if born in a poorer town.

As Prime Minister, Mr Brown has appealed above politics, across party, to a unity of national purpose. But he cannot achieve the progressive consensus he seeks if he only says things with which nobody could disagree. A catch-all consensus will lack progressive content. "Punch and Judy" politics puts people off, but spelling out a political vision will sometime require a willingness to divide, as Brown puts his Labour case to a public audience.

Authenticity is becoming an ever more valuable political commodity. Political values are central to the authentic Gordon Brown. The vision thing depends on "letting Gordon be Gordon" – that means letting Gordon be Labour, too.

The writer's Fabian pamphlet The Vision Thing can be read at www.fabians.org.uk